ils ne laisseront

they won't let; they won't leave

→ il
phrase Rare #37,058
they won't let; they won't leave This is the future tense of laisser with negation. Before an infinitive, it usually means “they won’t let” someone do something; with a direct object such as leur terre, it means “they won’t leave” or “abandon.”
FR: Ils ne laisseront pas les enfants jouer dehors.
EN: They won't let the children play outside.

Ils ne laisseront pas Tom s'échapper.

They won't let Tom escape.

Ils ne laisseront pas sortir Tom.

They won't let Tom out.

Ils ne laisseront jamais leur terre.

They will never abandon their land.

— Avatar (2009)

Ils ne laisseront pas Tom entrer.

They won’t let Tom in.